1. Field of the Invention
The present invention relates to workholding apparatuses and, in particular, to a device for holding two work- pieces relative to a known reference location which is capable of sequentially holding and releasing the workpieces.
2. Description of the Invention Background
As the apparatuses for performing machining operations on workpieces have become more sophisticated, the need has arisen for the apparatus for holding workpieces during such machining operations to be functional so as to allow the complete benefit afforded by such modern-day machining apparatuses. One prior form of workpiece holding apparatus is disclosed in Krason, et al., U.S. Pat. No. 4,529,183, issued July 16, 1985, entitled "Method of Machining and Vise for Use Therein". In that patent, apparatus was disclosed for holding two workpieces, each with respect to a fixed reference location. However, I have discovered that such apparatus may be improved to provide greater even utility to the machinist.
The workholding system described in the above-mntioned patent incorporates a base member having a central jaw member secured thereto. A slide assembly is provided first slide and a second slide, each mounted on the base for sliding movement, and a screw shaft for coupling and moving the slide members. As such, that apparatus provides a free-floating clamping assembly relative to the central jaw member. In the operation of such apparatus, when one workpiece or part is clamped between one slide member and the fixed jaw member, an operator would normally use one hand to hold the workpiece and the other to turn the screw shaft to advance the slide relative to the first workpiece. Unfortunately, because the operator's hands are engaged in the above-described activities, he does not have a free hand available to place another part between the other slide member and the central jaw. If the one part was released to position the other part, then the one part could be displaced from its workholding position, assuming that the friction inherent in the vise is insufficient to immobilize the one slide member. Therefore, I have discovered the need for a mechanism to act as a "third hand" for the operator to allow for the positioning of the workpieces and the simultaneous operation of the screw shaft.
Another shortcoming with the prior workholding system relates to the removal of the workpieces from the workholding system. It will be appreciated that when the screw shaft is rotated, both parts will simultaneously be released. As such, and especially if the work holding system is disposed in a nonhorizontal configuration, when one hand of an operator is used to rotate the shaft, the other hand may only remove one part while the other part may unintentionally drop from the workholding system, possibly damaging the costly, machined part.
One prior art apparatus which, perhaps unintentionally, alleviates certain of the aforementioned problems is produced by Kurt Manufacturing Company under the trademark DOUBLE LOCK. In such apparatus, a lockable collar is attached by means of bearings to one extended end of the screw shaft. The collar is then spring biased relative to the base member. In the operation of such apparatus, the sequential engaging and release of workpieces may, to some extent, be accomplished. However, because the collar is attached to one end of the screw shaft and means are provided intermediate the locking collar and the base, the overall length of the work holding system is unnecessarily increased. Those skilled in the art will appreciate that due to the plethora of functions performed by the many machining elements of modern machine tools, a large workpiece holding apparatus interferes with the desired functioning of the machining apparatus and serves as a limitation on the size of workpiece which may be accommodated.
The subject invention is directed to an improved apparatus for holding two workpieces relative to a fixed location which overcomes, among others, the above-described problems and provides a vise which may engage one workpiece and retain it prior to another, and may release one workpiece while retaining another, and which is of a compact size so as to minimize interference with machining operations.